CrowTalk

CrowTalk

Corvus cornix

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🗺 Regional sounds: Crow dialect varies between populations. Always note the location when saving — your recording contributes to local dialect research.
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What to observe month by month — Hooded Crow in suburban Stockholm
❄️
January
Winter flocking · food dependency

Crows gather in larger groups for winter protection. Deep snow covers natural food, making them more dependent on supplementary feeding. A core family group of 12–13 individuals may adopt a regular feeder as part of their territory — numbers can swell to ~30 when neighbouring crows join.

What to watch for
Large mixed flocks (crows + jackdaws) in open areas
Cooperative foraging — individuals signal food finds to the group
Crows flying to greet you when you appear with food
Pair bonds visible even within the flock
🌨️
February
Pre-spring restlessness · hierarchy visible

Large flocks of crows and jackdaws cross the sky — increased activity despite remaining snow and cold. A clear hierarchy becomes visible: older, larger crows act as "group leaders" deep in the forest, signalling which direction the flock should fly when food is found. Territory thinking begins to form.

What to watch for
Directed flock movements — follow a lead bird from a forest edge
Pairs beginning to separate slightly from the main flock
Increased vocalisation near potential nesting sites
First signs of courtship: bowing, preening each other
💨
March
Nest building · storm flying

First signs of spring. Storms become a playground — crows use strong winds for acrobatic flying, sometimes in pairs, sometimes in groups. Their flight over open fields looks like a dance. Flock sizes decrease as pairs establish territories. Food caching becomes more frequent as individuals compete.

Late March: nest construction begins. Pairs select a tree, often at height, and start building. In Årsta, one pair nests at 6th-floor height, visible from an 8th-floor apartment.

What to watch for
Acrobatic flying in wind — barrel rolls, sudden dives
Pairs carrying sticks and twigs to nest sites
Food caching: crow buries excess food, smooths surface with bill
Smaller groups — territorial pairs dispersing
🌸
April
Incubation begins · interspecies conflict

Crows are seen in established pairs. Females sit tight on the nest, resting heavily before egg laying. Multiple nests visible in neighbourhood trees. Other species become aggressive: fieldfares (björktrastar) defend territory against crows and will dive-bomb them — sometimes in coordinated attacks. Ravens appear sporadically and displace local crows from their territory.

What to watch for
Female sitting low on nest, barely visible
Male foraging alone and returning to the nest area
Fieldfare attacks on crows — watch crows crouch and flee
Crows escorting ravens out of territory
🌿
May
Hatching · chick care

Large winter flocks are gone. Pairs focus on their own family and territory. Early May: first chicks hatch. The female broods while the male forages. Eggs: up to 6, pale blue-green with liver-brown spots, ~45×30 mm. Warning calls (3 fast calls) sound when a fox, crow or raptor approaches the nest.

Gulls and herring gulls become the primary aerial threat in the upper airspace during this period.

What to watch for
Male making multiple food trips per hour
Female rarely leaving the nest
3-call alarm (rapid KRA-KRA-KRA) when predators appear
Only one crow from the pair visible at a time near the nest
☀️
June
Fledglings · first flight

Around June 1, the first fledglings leave the nest. They are already large but cannot fly — they jump on the ground and cling to bicycles and fences. Juveniles are recognisable: duller plumage, slightly lighter, softer bill, blue eyes and swollen gape corners. They beg loudly with raised wings when a parent approaches.

By day 9, a chick may fly 10 metres up into a tree. The male grows bolder, following the observer further from the nest. Both parents feed young. Tragically, traffic and gull attacks take some fledglings.

What to watch for
Juvenile: blue eyes, pink gape, wobbly posture
Begging call — high-pitched, loud, constant
Parent caching food 20 m away for later retrieval
Both parents calling (4 soft calls) after feeding — contentment
Magpies and gulls hunting fieldfare chicks nearby
🌞
July
Summer dispersal · teaching

Crows seem to disappear during daytime. Activity shifts to early morning (from ~06:00). Juveniles are still with parents, being taught foraging and territory skills. The family may range more widely now that chicks can fly. Historically reported that some crow populations move toward Åland and the islands in summer — hard to verify.

What to watch for
Juveniles following parents — still begging but less insistently
Family groups of 4–5 birds moving together
Best observation window: early morning, same spot daily
One juvenile may be slower to develop than siblings
🍒
August
Juvenile independence · pre-autumn

Continued development of juveniles. Late berries, insects and small animals provide ideal training prey. Parents demonstrate tool use, food handling and caching. The juvenile grows gradually more independent — exploring alone but returning for support. Parents may begin reinforcing or scouting next year's nesting site.

What to watch for
Juvenile foraging independently for short periods
Juveniles practising bill manipulation: opening packages, probing cracks
Parents watching from distance while juvenile forages
Increased interactions with neighbouring crow families
🍂
September
Thermals · aerial competition · mobbing

Autumn felt clearly. Large flocks circle industrial areas, using thermals from heated asphalt and flat rooftops. Crows and gulls compete for the same airspace with different strategies: gulls dominate in calm weather with their long wings; crows dominate in gusty autumn wind with their compact, manoeuvrable wings.

September 25 (Årsta): a long-eared owl was chased into a tree by crows and jackdaws, terrorised for hours by magpies that plucked its tail feathers. This "mobbing" behaviour drives predators from nesting areas and is one of the corvids' key collective defence tools.

What to watch for
Thermals: crows circling in tight spirals above industrial areas
Mobbing events: multiple crows dive-bombing a raptor or owl
Intense food caching before first frost
Juvenile vocal development — calls becoming stronger and more varied
🌬️
October
Storm play · nut cracking · flocking

Dramatic autumn weather. Crows "play" in storms — acrobatic flying high in the wind strengthens flight muscles ahead of winter. Flocking increases: restless groups of young crows move across the city in preparation for winter. In southern Sweden, crows have been observed placing walnuts on roads and waiting for cars to crack them open, then retrieving the kernels — a learned cultural behaviour spread through observation.

What to watch for
Storm flying: barrel rolls and tumbles in strong wind
Road nut-cracking: crow drops hard food on traffic lanes
Large restless flocks crossing the city
Fallen fruit scavenging — apples, rowan berries
🌧️
November
Winter movement · urban foraging

Crows from further north (including possibly Åland) may arrive on the Swedish mainland as conditions worsen. Those staying intensify urban foraging — raking through fallen leaves and checking bins. Social dynamics grow more complex: competition for limited resources increases aggression between individuals. Migration, if it occurs, typically happens flockwise from October onwards, preferring calm or light tailwind conditions.

What to watch for
Unfamiliar individuals appearing in established territories
Displacement fights at reliable food sources
Leaf-raking behaviour to expose insects and seeds
Large communal roosts forming at dusk in tall trees
🌃
December
Winter roosts · Christmas surplus

Urban crows in Stockholm adapt well to the city's warmth. Foraging around restaurants and bins intensifies — the Christmas season's increased food waste is a key resource. Large winter roosts form in trees near heat sources (ventilation shafts, heated buildings). Territorial disputes increase as natural food sources shrink and competition with other wintering species grows.

What to watch for
Winter roosts: dozens of crows gathering at dusk in the same tree
Active bin and skip foraging, especially near restaurants
Crows near ventilation exhausts and other urban heat sources
Established pairs staying close — pair bond maintained through winter
🎵 Vocalisations
Social
Contact call
kraa… kraa (1–2 calls)
Soft, calm call to maintain contact with flock or partner. The most common call in everyday situations. Longer pauses between calls signal relaxation.
Food
Food call
kra-kra-kra (2–3 short)
Shorter, faster calls when food is found. Research shows crows deliberately keep food calls shorter to avoid attracting too many competitors (Pendergraft & Marzluff, 2019).
Alarm
Alarm call
KRA! KRA! KRA! (3 fast)
Three fast, loud calls when a raptor or other threat is detected. Universally understood by other crows. WARNING: May cause a permanent negative association if used against crows that don't know you.
Alarm
Mobbing
KRA-KRA-KRA-KRA-KRA (5+ calls)
Intense, repeated calls to rally the flock against a threat. Five or more calls mobilise the entire flock. Crows remember faces and can spread "warning" to others (Cornell Lab, 2012).
Regional
Territorial
KRAAAA (2 long, powerful)
Powerful, extended call to defend territory. Used mostly during breeding season. Shows clear variation between regional populations — an important sound for dialect research.
Social
Rattle / Click
klk-klk-klk (low frequency)
Low-frequency clicking or rattling sound. Used in close social contact, often between pairs. A sign of relaxed trust — a good sign if a crow rattles near you.
Juvenile
Juvenile call
high-pitched, uncertain
Young crows have a thinner, higher-pitched voice. Adult crows are usually tolerant of begging juveniles. Juvenile calls are regionally inconsistent — dialect develops during the first year of life.
Comfort
Content / Comfort call
kraa-kraa-kraa-kraa (4 soft)
Four soft, calm calls used in safe situations — resting, near a partner, or after successful feeding. Similar to contact call but with longer duration per call.
🔢 Call count
CountMeaningSituation
1Acknowledgement / attentionReply to contact, "I see you"
2Contact / greetingCalm presence, near partner
3Alarm — threatRaptor, unknown human
4Content / well-beingSafe situation, bonding
5+Mobbing — rally flockIntense threat, chasing raptor
2–3 shortFoodFood find, but kept sparse
2 longTerritorialTerritory defence, breeding season

Counting: A 2024 study in Science showed that crows mentally plan 1–4 calls before vocalising — one of the few documented forms of numerical planning in birds.

🐦 Body language
⬆️
Upright posture, feathers sleek
Alert or alarm behaviour. The crow is focused on a potential threat. Often combined with alarm calls.
⬇️
Hunched, ruffled feathers
Relaxed and calm state. Ruffled feathers = thermoregulation or relaxation. A good sign if the crow hunches near you.
🙇
Head-lowering (allopreening)
The crow lowers its head towards a partner for preening. A sign of deep trust and social bonding. Rare towards humans, but documented.
🍗
Flying towards you + wing flapping
Begging behaviour, common in juveniles towards parents. Towards humans = established relationship and expectation of food.
🎁
Leaving objects
Documented behaviour in crows that have formed close bonds with humans. Considered reciprocal gift-giving — the crow returns the favour for food received.
👁️
Direct eye contact + sideways posture
Crow eyes are on the sides of the head. Tilting to look directly with one eye = focus and curiosity. Avoiding eye contact = discomfort.
💬 Communicating with crows

Core principle: Crows are highly social and curious, but also cautious. Build trust gradually. A crow that trusts you will actively seek you out.

1
Establish a safe place
Visit the same spot at the same time each day. Leave food (walnuts, unsalted peanuts, soft food) without trying to interact. Let the crows observe you undisturbed for 1–2 weeks.
2
Start with contact calls
Once the crows are used to you: play a soft contact call (1–2 calls) via the app. Wait 30–60 seconds. If they respond or move closer — repeat. Never play alarm or mobbing at this stage.
3
Record responses
Record the crow's response directly in the app (Record tab). Note call count, character and behaviour in the journal. Patterns over time reveal whether you are classified as friend, neutral or threat.

⚠️ Never use alarm or mobbing against unfamiliar crows. A crow that classifies you as a "threat" shares that information with its flock. This negative association can persist for months to years and is very difficult to reverse.

Exception: Alarm can be useful if you want to study reaction patterns — but only with crows that already know you well and can see that it is you playing.

🗺️ Regional dialects

Hooded crow (Corvus cornix) vocalisations show measurable acoustic differences between populations. Studies across Scandinavia, Central Europe and the Mediterranean have documented systematic variations in fundamental frequency, call duration and modulation patterns.

Why this matters to you: A crow in your region may not respond appropriately to a recording made in another country. The app includes recordings from xeno-canto — note the recording's country of origin for each XC sound.

Your role: Every recording you make and tag with a location contributes to mapping regional dialects. Share data via the JSON export.

Tip: Always record the crow's response immediately after playing a sound. Comparing the sound you played with the crow's reply is the core of dialect research.

👤 Facial recognition

Research at the University of Washington (Marzluff et al., 2010) showed that crows (Corvus brachyrhynchos, likely applicable to C. cornix as well) are capable of individual facial recognition in humans.

The experiment: Crows were trapped by researchers wearing a specific mask. Afterwards, crows reacted aggressively specifically towards that mask — not others. The reaction also spread to crows that were not present during the trapping.

Memory: Negative associations were still observed 5 years later. Positive associations appear to build more slowly but are equally lasting.

Practical conclusion: Crows in your area recognise your face. Always wear similar clothing during contact sessions to reduce confusion. Hats and glasses can interfere with recognition.

🔗 External resources
🌿 Artportalen — Swedish species observation database. Report your crow observations here.
🐦 Merlin Bird ID — Cornell Lab AI bird identification. Great for verifying species in the field.
🎵 Xeno-canto — Crowdsourced bird sound library. Source of XC recordings in this app.
🧠 Intelligence & cognition

Corvids (crows, jackdaws, ravens, rooks) belong to the family Corvidae and rank among the most cognitively advanced animals on Earth. They learn new sounds throughout life, cooperate, use tools, and may be capable of empathy.

Neural density: The raven's pallium contains up to 14× more neurons per gram than the human cerebral cortex. A 2020 study in Science showed that bird brains are structurally more similar to mammal brains than previously thought — with long-range associative circuits comparable to the neocortex.

Raven development: A 2020 study in Scientific Reports found that hand-raised ravens tested at 4 months perform comparably to adult great apes on cognitive tasks — suggesting rapid and near-complete cognitive maturation very early in life.

Mourning the dead: Research by Dr Kaeli Swift (University of Washington) documented corvids gathering in large groups around dead flock members, leaving objects (sticks, feathers) at the body, and following the corpse for days. Brain scans showed activation of threat-memory regions — suggesting these gatherings serve a functional purpose: learning about danger from the manner of death.

Old field observation (Shetland Islands, 1888): About 50 crows were seen gathered on a field in what looked like a "court". One crow stood apart as if on trial. After a period of intense calling it crouched, appearing to beg for mercy — and was then executed by the flock, which scattered immediately. Such reports of apparent collective social judgment have been noted across multiple historical sources.

✂️ Crow training

Because crows learn quickly and retain information long-term, positive reinforcement training is effective. The key is consistency, patience, and a reliable reward delivered immediately after the desired behaviour.

Behavioural researcher Christian Gunther-Hanssen developed a pilot project in Södertälje where crows were trained to collect cigarette butts in exchange for food from a vending machine — a project that became international news. The principle can be applied to any retrievable object.

1
Establish a food relationship first
Before any training, build a reliable feeding routine (same time, same place, same signal). The crow must associate you with reward before it will engage with training tasks. This phase takes 1–4 weeks.
2
Introduce the target object
Place the target item (e.g. a cigarette butt, a coin, a marked stone) near the feeding spot. Reward the crow any time it approaches or touches the object — even if it just investigates it. Use a short, repeatable reward sound (whistle or click) immediately at the moment of correct behaviour.
3
Shape pick-up behaviour
Reward only when the crow picks up the object. Do not reward approach alone. Place multiple objects on the ground; reward each pick-up. Crows are fast learners — expect to see deliberate pick-ups within days once the association is formed.
4
Add a deposit location
Place a small container (bowl, box) near the feeding point. Reward the crow only when it drops the object into the container. Start with the container directly below where the crow normally lands; gradually move it to a fixed permanent location.
5
Increase difficulty gradually
Scatter objects at different distances and heights. Introduce similar-looking non-target items; only reward the correct object. The crow will learn to discriminate. Once reliable in one environment, test in different weather and lighting conditions.

Never use punishment. Crows have a long, precise memory for negative experiences. A single bad encounter can undo weeks of trust-building. If a session goes poorly, simply end it — do not withhold food as punishment.

Whistle cue: Establish a consistent whistle or sound before presenting food. Over time the whistle alone will bring crows from considerable distance — useful for calling them to a training session.

🐾 Enemies & mobbing

Natural enemies include eagle owls and hawks. However, crows in groups can overwhelm and kill a hawk that attacks a nest — and have been documented burying the carcass under branches afterwards. Mobbing behaviour (coordinated harassment of a larger predator) is one of the corvid family's most sophisticated collective defence strategies. Crows on Stockholm's bridges have been seen circling eagles passing through their territory.

Other species also mob crows: fieldfares (björktrastar) are particularly aggressive during their own breeding season and will dive-bomb crows repeatedly, sometimes even depositing droppings on them in flight.

📚 References
Marzluff, J.M. et al. (2010). Lasting recognition of threatening people by wild American crows. Animal Behaviour, 79(3), 699–707.
Pendergraft, L.T. & Marzluff, J.M. (2019). Crow vocalizations: complexity and context. Behavioural Processes, 163, 78–89.
Nieder, A. et al. (2024). Crows count before they vocalize. Science, 383, 1058–1061.
Clayton, N.S. & Dickinson, A. (1998). Episodic-like memory during cache recovery by scrub jays. Nature, 395, 272–274.
Emery, N.J. & Clayton, N.S. (2004). The mentality of crows. Science, 306, 1903–1907.
Cornell Lab of Ornithology (2012). Crow behavior and vocal communication. Birds of North America Online.
xeno-canto Foundation (2024). Corvus cornix recordings. xeno-canto.org. CC BY-NC-SA 4.0.
Olkowicz, S. et al. (2016). Birds have primate-like numbers of neurons in the forebrain. PNAS, 113(26), 7255–7260.
Kabadayi, C. & Osvath, M. (2017). Ravens parallel great apes in flexible planning for tool-use and bartering. Science, 357(6347), 202–204.
Swift, K.N. & Marzluff, J.M. (2015). Wild American crows gather around their dead to learn about danger. Animal Behaviour, 109, 187–197.
Güntürkün, O. & Bugnyar, T. (2016). Cognition without cortex. Trends in Cognitive Sciences, 20(4), 291–303.
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